As for a color reproduction system for making color photographs, a subtractive color system has generally been used. The subtractive color system is to obtain a color image in such a manner that yellow, magenta and cyan dyes are each formed upon coupling reaction of couplers with the oxidized products of a color developing agent produced when silver halides are reduced, by making use of a color developer, in each of blue-sensitive, green-sensitive and red-sensitive emulsion layers which are exposed imagewise to light.
As a magenta color-image forming coupler, a 5-pyrazolone type coupler has popularly been put to practical use and the wide ranging studies thereof have been made so far. However, the dyes formed of the 5-pyrazolone type couplers have caused degradation of color purity, because they have had a undesirable absorption having in the blue region of the spectrum.
To solve the above-mentioned disadvantage, there have been the proposals of various types of couplers such as those of the pyrazolobenzimidazole type, indazolone type, pyrazolotriazole type, pyrazolopyrazole type, and pyrazolotetrazole type.
In fact, the dyes formed of those proposed couplers have been preferable from the viewpoint of color reproduction. In recent years, therefore, pyrazoloazloe type couplers have been put to practical use.
This type of couplers are, however, expensive in production cost and not so satisfactory in characteristics from the viewpoints of color forming efficiency and graininess. It has, therefore, been desired to improve these disadvantages.
On the other hand, there have been well-known compounds, as is described in, for example, Angew. Chem. Int. Ed. Eng (2) (1983) 191-209. The Theory of The Photographic Process 4 Ed p338. such compounds are capable of reacting with the oxidized products of a developing agent to form an azine dye through a cyclization-reaction so that magenta color may be developed. Such compounds are preferable from the viewpoint of color reproduction because the spectral absorption of the azine dyes themselves are sharp. However, these compounds are serious in color contamination because their color forming efficiencies are low and their color forming reaction does not go all the way. Therefore, a further improvement has been required so far.